Newsletter #305

This week, I'd like to take a closer look at an exciting new trial examining the effects of supplementation with specific carotenoids on the central nervous system.

Lutein and its isomers, zeaxanthin and meso-zeaxanthin, are best known for their propensity to accumulate preferentially in the retina, making up the macular pigment. Macular pigment acts as an optical filter for blue light, and provides protection against oxidative stress to ocular tissue, so it’s obviously super important for the eyes.

However, macular pigment is also correlated to cognition, perhaps because lutein has been shown to cross the blood-brain barrier, and build up in the hippocampus and other regions of the brain.

These benefits have already been demonstrated convincingly in adults, however there is reason to believe that children could profit as much or even more from supplementation with lutein and zeaxanthin.

For one thing, the human body cannot synthesize lutein or zeaxanthin, and dietary intake of these carotenoids is not especially high. American adults are estimated to take in only about 1-2 mg per day, and children get only half that dose. Given that the best dietary source of lutein and zeaxanthin is leafy green vegetables, this shouldn't be too surprising! And you can imagine that a developing human brain might have greater need, as 90% of our brain growth transpires before we reach the age of five.

No studies have examined the impact of macular xanthophyll supplementation on cognitive function in kids – until this one. Let's take a look.

Prior research in healthy young adults, as well as in the elderly, have demonstrated improvements in cognitive and visual function in response to supplementation of macular xanthophylls, which in turn could be linked to increased levels of these pigments in the retina.

To explore whether similar benefits could be elicited earlier in life, Indian researchers recruited 60 children in Bengaluru (age range of 5-12), and randomly assigned participants to take either a combination of lutein (10 mg) and zeaxanthin (2 mg) or placebo every day for six months.

Before and after the trial, researchers assessed macular pigment optical density. This refers to the density of macular pigment in the center of the retina, which protects your eyes from blue light and other forms of radiation. It is also a way to objectively measure levels of lutein and zeaxanthin, since those carotenoids make up the macular pigment.

The researchers also took blood work to capture blood levels of lutein and zeaxanthin, as well as brain-derived neurotrophic factor (BDNF), a protein that plays a key role in learning and memory. Finally, the researchers administered tests to the kids to assess levels of eye strain and fatigue, as well as a battery of cognitive tests.

After 180 days, the group that took lutein and zeaxanthin showed a massive rise in serum levels of lutein and zeaxanthin (from a mean of 96.9 ng/mL up to 1246 ng/mL!), which was accompanied by a ~25% increase in macular pigment optical density, compared to placebo.

All of which suggests that the gummies were being well-absorbed, and their active constituents were getting successfully integrated into tissues of the central nervous system where they belong.

Importantly, that increased macular pigment appeared to enhance natural shields against the punishing effects of light from digital devices, as the kids in the treatment group also showed decreased eye strain.

That's great news, since children's eyes are more sensitive to the effects of bright light, and they may be getting exposed to more of it than ever before; surveys show that more than 80% of kids spent at least three hours daily looking at light-emitting screens.

The most exciting impact of the supplement, however, was on their brainpower: The kids in the experimental group experienced an array of improvements in various parameters of cognitive function, including processing speed, focus and concentration, memory and learning, and visuospatial working memory.

Finally, the supplement appeared to enhance levels of brain-derived neurotrophic factor, at least in circulation.

At the start of the study, the kids in the control group actually had higher serum BDNF than the lutein + zeaxanthin group. However, after 180 days of supplementation, BDNF levels in the treatment group were significantly higher compared to placebo (31.03 ± 3.47 ng/mL for lutein/zeaxanthin, versus 13.61 ± 5.88 ng/mL for placebo).

The increase in BDNF is notable because of its role in promoting learning, memory, and neural processing speed. But why would lutein and zeaxanthin boost levels of BDNF?

It’s not entirely clear. However, prior research has shown that supplementation with these pigments is reliably connected to reductions in markers of inflammation, as well as increased antioxidant capacity. It has been shown that inducing inflammation experimentally can lower BDNF, and conditions associated with neuroinflammation seem to commonly coincide with lower levels of BDNF. It’s reasonable to speculate that lutein and zeaxanthin were dampening a cascade of inflammation in these kids, which could facilitate greater production of BDNF and the observed improvements in cognition.

And this may be especially relevant for children. We often talk about the toll of oxidative and inflammatory stress on the brain in the context of aging. However, oxidative stress and inflammation may have a disproportionately great impact on a developing brain, and the price of exposure to these stressors may reverberate throughout their lives.

When woodpeckers are foraging for bugs, their heads bash into tree trunks at a blinding speed, decelerating with each impact at around 1,000 times the force of gravity (1000 g).

This would easily kill a human, but woodpeckers are able to absorb the blows with no apparent harm, and they can drum like this literally thousands of times per day. The secret to this shock absorption lies deep inside their heads, actually in their mouths. Woodpeckers have astonishingly long tongues, close to a third of the length of their body, to help them reach for food hidden inside of trees. That tongue is supported, like in humans, by the hyoid bone.

However, because of the insane length of their tongue, their hyoid bone wraps entirely around the woodpecker’s skull, forming a sort of internal storage unit. When the muscles around the hyoid bone contract, it helps secure the skull, almost like a seatbelt around their brain!

I’ve been purchasing this product for several years, mainly because I used to have major issues with computer eye strain (seems to be largely resolved now), but also because I was impressed with the growing literature related to potential cognitive benefits, like the study described above.

If you’re looking for a gummy version, this product looks comparable. I haven’t used it, but it was tested by the friendly folks at ConsumerLab and was found to be legit.

We know that consuming a nutrient-rich diet is key for performing at your very best. One efficient and convenient way to ensure that you’re making that happen on a daily basis is through smoothies.

Notably, some studies suggest that green smoothies may be one of the best ways to acquire macular xanthophylls in the diet.  Research has shown that blending green leafy vegetables liberates lutein and other carotenoids from the cells of these plants, making them substantially more bioavailable to your body.

This course takes a deep dive into phytochemicals in plants, where they are found, their powerful health effects, and how intelligently-devised smoothies can help optimize our intake of these awesome compounds. For a practical breakdown on building nutritious smoothies, please refer to our How-to Guide for smoothies.

Wishing you the best,

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